1. Technical Field of the Invention
The present invention relates to an electromagnetic switch, more particularly to a so-called connector type electromagnetic switch for a starter motor of an internal-combustion engine to control electric power to the motor.
2. Description of the Related Art
Engine starters are commonly used to start internal-combustion engines mounted on vehicles. An engine starter includes a motor (hereinafter called as a starter motor) as a driving source to start an internal-combustion engine.
The starter motor has an electromagnetic switch to control electric power. The electromagnetic switch includes a coil for energizing and a contact mechanism for connecting and disconnecting an electric power to a subsequent element.
The coil energized by the electric power generates a magnetomotive force that connects and disconnects the contact mechanism. The connection and disconnection of the contact mechanism controls electric power to the starter motor.
More specifically, the electromagnetic switch includes a switch coil that is connected to an ignition switch through a switch terminal. Once the ignition switch is turned on, the switch coil is supplied with a current from a battery and serves as an electromagnet.
A plunger, a ferromagnet, is slidably disposed inside the switch coil. Once the electromagnet is formed, an attraction force between a fixed iron core provided to a magnetic circuit of the electromagnet and the plunger is generated. This causes the plunger to move toward the fixed iron core, which thereby closes the main contact of the starter motor.
On the other hand, once the ignition switch is turned off, the current flow to the switch coil is interrupted. This acts to extinguish the attraction force acting between the fixed iron core and the plunger, causing the plunger to be pushed back by the compressive force of a return spring, thereby opening the main contact.
The switch terminal includes two types: one type is a so called “bolt type” switch terminal in which an electric conductor is fixed with a nut; the other type is so called a “connector type” switch terminal in which the electric conductor is connected with a connector formed at a tip end of the electric conductor.
The former switch terminal is disclosed in Japanese Patent Application Laid-Open Publication No. 2006-286258. The electromagnetic switch disclosed in this Patent Publication is constructed in such a manner that a head portion of a bolt of the switch terminal is insert-molded in a case of the electromagnetic switch, and a shaft portion of the bolt projects outwardly from the case.
The bolt is connected to one end of a coil inside the case, electrically conducting to the coil. One end of the electric conductor connected to the ignition switch forms a wire connection portion. The wire connection portion is tightened by the nut to the shaft portion of the bolt, thereby fixing the electric conductor to the switch terminal.
The latter electromagnetic switch, the connector type electromagnetic switch, is disclosed in Japanese Patent Application Laid-Open Publication No. 2006-177160. The electromagnetic switch in this Patent Publication includes a metal connector for a switch terminal that is inserted in a case and is connected to one end of the coil.
A part of the metal connector projects outward from the case. The metal connector has such a male connector member integrally formed with the case that accommodates an outer periphery of the portion of the metal connector projecting outward from the case.
The male connector member is adapted to engage with a female connector member. The female connector member is formed at an end portion of an electric conductor that is connected to an ignition switch. The engagement between the female connector member and the electric conductor allows the electric conductor to be electrically connected to the switch terminal.
Vehicles with electrical failures in every day life may be subject to testing of the electrical connections in order to determine its cause. The test may be conducted by applying a tester terminal to a conductive portion between the wiring and a terminal of each piece of equipment in order to determine electrical connections and contact resistance.
This testing also determines an electrical connection of the electromagnetic switch of an engine starter. In this testing, a bolt type switch terminal allows the tester terminal to make a direct contact with the terminal with the wiring kept connected, because it has a portion exposed near the wire connection portion. However, the connector type switch terminal was not able to allow the testing with the wiring kept connected, because the terminal does not have an exposed portion.